Electric switch



Nov. 49, 1948. G. c. CROWLEY ELECTRIC s wI'rcH Filed April 15, 1947lvnvenbor: George C. Crow/leg.

by W W Hss ther-neg.

Patented Nov. 9, 194s ELECTRIC SWITCH George C. Crowley, Bridgeport,Conn., assignor to General Electric Company, a corporation of New YorkApplication April 15, 1947, Serial No. 741,560

(Cl. ZOO-16) 1 Claim.

. l The present invention relates to electric switches of the typewhereby a plurality of circuit connections may be established forcontrolling the operation of a device, such as for controlling the speedof a motor or the heating of a heating device such as an electricheating pad. More particularly, the present invention relates to slidetype switches and to so-called through switches. p

It is an object of the present invention to provide a switch of theaforementioned type which is simple, rugged, and which can bemanufactured at a low cost.

An embodiment of the present invention is shown in the accompanyingdrawing in which Fig. l is an enlarged perspective view of my switchwith a portion of the cover broken away to disclose some of theoperating mechanism; Fig. 2 is a partial vertical section takenlongitudinally through the central portion of the switch; Fig. 3 is asection taken along the line 3-3 of Fig. 2; Fig. 4 is a plan view of theswitch with the cover removed; Fig. 5 is an enlarged perspective view ofthe movable brush; and Fig. 6 is a schematic wiring diagram of my switchconnected to an electric heating pad.

As shown in the drawing, my switch has a hollow housing comprising abase member I and a cover member 2, both made of insulating material andpreferably of a molded plastic. Both base and cover are partly cut awayat the ends as at 3 and 4 to form an aperture for the entrance ofconnecting wires.

The base of the switch, which is substantially a hollow shell, isprovided with upwardly extending bosses 5 and 6 having apertures I and 8therein adapted to receive the screws 9 and Ii) for holding the base andcover in assembled relation. The bosses 5 and 6, which are located alongthe longitudinal axis having inwardly extending shoulders II and I2. Twoinwardly and upwardly extending bosses I3 and I4 are also provided atthe sides of the base. These latter bosses have ilat surfaces of thesame height as the shoulders II and I2.

Fitted on top of the shoulders II and I2 and the bosses I3 and I4 is aninsulating contact carrying plate I5. Mounted on the plate I5 are aplurality of stationary contacts which are adapted to be connectedtogether by a movable contact mounted in the cover as will be describedlater. All circuit connections to my switch are made to the stationarycontacts and preferably on the under side of the plate I5. In the'embodiment of my switch as shown in the 2 drawing, the carrier plate I5is provided on its upper surface with three longitudinal rows of contactelements. The first comprises a conducting bar I6. The second rowconsists of three contacts Il, I8, and I9 while the third row has twocontacts 20 and 2l. The contact bar I6 and the other contacts may besecured to the carrier plate I5 in any desired manner. I prefer,however, to provide the bar I6 at its ends with right angled ears 22 and23 which are pushed through slots in the plate I5. The ear 23, in so faras no connections need be made to it, may be bent over the under side ofthe plate, while the ear 22, to which connection must be made, may begiven a slight twist. The remaining contacts I'l to 2| are preferablyformed by the heads of rivets fastened to the plate I5. Contact I1 holdsin place underneath the plate I5 a short metal strip 24 having adownwardly projecting ear 25 provided with an aperture 26 tc which awire connection may be fastened as by soldering. Contacts I8 and I9 areconnected together by a metal bar 2'! mounted beneath the plate I5 andhaving at one end a wire connection ear 28. Similarly, the contacts 28and 2l are connected together beneath the plate by a bar 29 having aconnection ear 30. There is also mounted beneath the plate I5 aconducting bar 3l secured to the plate by rivets 32 and 33 whose headsare recessed in the plate as shown in Fig. 2. The bar 3l has wireconnection ears 34 and 35 at its ends.

All connections to the switch are made to the contacts on the plate I5.As shown in Fig. 6, two line conductors 36 and 31 may be connected tothe bars I6 and 3l at the ears 22 and 34 respectively. Four wires 38.39, 40. and 4I may be connected to the controlled device as, forexample, the heating pad 42. Conductor 38 may be connected to contactsI8 and I9 by being soldered to the ear 28 of bar 21; conductor 39 tocontact I1 at the ear 25; conductor 40 to contacts 20 and 2I at the ear30 on bar 29; and conductor 4I to bar 3| at the ear 35, thus providing athrough connection from one side 31 of the line to the controlleddevice. The operation of the circuit in Fig. 6 will be further describedbelow.

Referring now to the movable Iswitch element which is mounted in thecover, it will be seen from the drawing that the cover 2 is providedwith a centrally disposed longitudinal slot 43. Projecting upwardthrough the slot 43 is an operating member 44 preferably made of metal.The member 44 is fastened to an insulating movable contact carrier 45,preferably by being molded directly into it. An operating knob 46 ispressed on the'member the cover 2.

The movable contact carrier 45 is U-shaped in transverse section. Itconsists o! two side members 46 and 41 which act as runners or slidersand bear against the upper surface of plate I near its outer edges. Therunners 46 and 41 are joined by a central bridging portion 48 whichsupports the actuating member 44 as described. To the under side of thebridging member 48 there is secured the movable contact 49 as by meansof rivets 48a. I'he movable contact 49, shown separately in Fig. 5,consists of a thin metal strip having three spring fingers 56, 5|.

and 52 positioned to bear respectively against the three rows ofcontacts on the plate I5.

To provide a snap positioning action for the slider, the upper surfaceof each of the runners 46 and 41 is recessed as at 53 along itstransverse axis. A small coil spring 54 surmounted by a ball bearing 55is inserted in each recess. The ball bearings 55 bear against fiat camsurfaces 56 in the nature of corrugated ridges formed one on each sideof the upper inner surface of the cover 2 and preferably moldedintegrally therewith. There are as many corrugations or notches 51 ineach ridge as there are positions for the switch. In the embodimentshown there are four circuit closed positions and one "oif position,making ve positions in all. When the assembly screws 9 and |0 arescrewed into the suitably located threaded holes 58 and 59 in the cover,the coil springs 54 are under compression. They thereby force the springcontact fingers 50, 5I and 52 downward against the fixed contacts andsimultaneously press the runners 46 and 41 against the plate I5.Longitudinal motion of the knob 48 thereby moves the spring contactslongitudinally over the various fixed contacts. The pressure of theballs 55 against the cam surfaces or corrugations 56 provides definitestop positions at each contact position.

The solid end portions of the cover 2 are provided with slots in whichthin insulating strips 65 and 66 are positioned. These extend across thewire entrance openings 3 and 4 at the ends of the switch and projectdownward into the hollow portion of the base I. If desired, the members65 and 66 may be made integral with the cover 2. The members 65 and 66provide a strain relief for the terminal connections of the wires, sincethe wires, in order to enter the switch, are thereby required to maketwo right angle bends as shown in Fig. 2. Therefore, no strain is placedon the soldered connections to the fixed contacts if the wires arepulled.

In the assembly wiring of my switch; it will be noted that thestationary contact plate I5 can be removed from the base and the wiresattached to their respective contacts. Thereafter the plate is laid backinto the base and the wires laid into the end cut-outs 3 and 4. Thecover 2, carrying the movable contact, is then placed on the base andpressed into contact with it, whereby the strain relief members forcethe wires to assume two right angled bends. With the fastening of screws9 and I0, the switch assembly is completed.

In the embodiment shown in the drawing which, by way of example, isspecifically directed to a. switch for the control of a heating devicesuch as the heating pad 42, four "heat and one on positions can beprovided. The four heat positions may correspond to low." medium mediumhigh, and high 44 on the outside of heat. It willbe noted 4 that in allbut the "ofi' position, the contact vi'lnger 52 is .always in contactwith the bar I4.

All three contact fingers are thereby connected to one side of thesupply line. In the low position of the switch, contact finger 5| makesconnection with fixed contact I8. In the medium" position, contactfinger 50 makes connection with fixed contact 2|. In the medium high"position, contacts 50 and 5| connect with fixed contacts and I8respectively. In the "high position contact 5| makes connection withfixed contact l1. Since the contact fingers are all connected together,the action is to connect the various stationary contacts I1 to 2|inclusive to one side of the supply line in the selective manner justdescribed.

When the switch is used to control the heating pad 42 shown in Fig. 6,the various control arrangements obtained are as follows: The heatingpad 42 has a single heating winding 66. One or more series safetythermostats 6| may be provided if desired. In addition, there isprovided a control thermostat 62 whose operation is governed by heatingresistors 63 and 64. These are so dimensioned in the local heat producedby them to cause the thermostat 62 to open its contacts and thereforetheheater circuit intermittently so as to maintain the desired temperaturein the heating pad.

In all positions of the switch the heating element 60, through conductor4| and switch bar 3|, is connected directly to one side 31 of the supplyline. Connection to the other side 36 of the supply line is made throughthe switch in the following manner: In the low heat position, conductor38 is energized; thermostat heater 63 is thereby connected in serieswith thermostats 62 and 6| and the heating winding 60, producing maximumlocal heat and causing thermostat 62 to open most frequently. In themedium position of the switch, conductor 40 is energized and thereby thecircuit is completed through thermostat heater 64 and thermostats 62 and6| to the heating winding 60. In the medium high position of the switch,both conductors 38 and 40 are energized, placing heaters 63 and 64 inparallel and together in series in the heating circuit; the parallelcombination dissipates less heat than either of resistors 63 or 64 aloneand, therefore, permits thermostat 62 to remain closed longer to give ahigher pad temperature. In the high position of the switch, conductor 39is energized, heaters 63 and 64 being entirely out of the circuit,whereby full current flows continuously through the heating winding 60unless interrupted by the safety thermostat 6|.

While I have described my invention by way of example as specificallyembodied in a heating pad switch, it will be evident to those skilled inthe art that my switch is equally adaptable to other wiring arrangementsfor heating devices, as well as to motor speed or direction controlcircuits. For these purposes a different arrangement of the fixedcontacts may be provided, if desired. Moreover, the movable brush may beprovided with as many contact fingers as required. In general, it willbe obvious to those skilled in the art that various changes andmodiflcations may be made without departing from my invention in itsbroader aspects and I, therefore, aim in the appended claim to cover allsuch changes and modifications as fall within the true spirit and scopeof my invention.

sans

whatlclaimasnewanddesiretosecureby Letters Patent of the United Statesis:

An electric switch of the through switch type comprising an elongatedhollow housing having wire receiving openings at both ends and formed intwo parts comprising a recessed base member and a cover member, astationary contact mounting element comprising a fiat insulating plate,means integral with said base member and extending upwards therefrom forremovably supporting said plate spaced from the bottom of said basemember, a plurality of rows o! sta tionary contacts on the upper surfaceof said plate, said stationaiy contacts having integral conductive meansextending through said plate and having terminal members on the lowersurface of said plate adapted to receive all wire connections forcircuits to be controlled by the switch, said cover member having alongitudinal slot formed therein, a movable contact carrier positionedbeneath the cover and having means extending through said slot to theoutside oi the cover for the operation of the carrier, a movable contacton said carrier comprising a spring contact nger having a total widthsuiiicient to span ali of said rows of stationary contacts, said movablecontact being mounted on said carrier in position to cooperate with saidstationary contaots for selectively completing circuits between them,said carrier having smooth bottom surfaces adapted to slide on the uppersurface of said plate, corrugated ridges extending inwardly from thesurface of said cover member, spring tensioned ball bearings mounted insaid carrier and positioned to bear against corrugations and thereby topress said movable contact against said stationary contacts, wherebysaid plate is held in position on its supporting means and there isprovided a snap positioning action as said carrier is moved, the numberof corrugations corresponding to the number of switch positions, andmeans holding said base and cover members together against the pressureof said movable contact and ball bearings.

GEORGE C. CROWLEY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS

